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General Biology: Basic Chemistry Concepts

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  • Element

    Element is a substance that cannot be broken down into other substances by normal chemical means.

  • Compound

    Compound is a substance consisting of two or more elements combined in a fixed ratio, with different characteristics than its elements.

  • Big Six Elements in the Human Body

    The Big Six elements are Oxygen (O), Carbon (C), Hydrogen (H), Nitrogen (N), Phosphorus (P), and Calcium (Ca), making up 99% of the matter in our bodies.

  • Atom and Subatomic Particles

    An atom is the smallest unit of matter retaining element properties, made of protons (+), neutrons (neutral), and electrons (-).

  • Atomic Number and Mass Number

    Atomic number is the number of protons; mass number is the sum of protons and neutrons in the nucleus.

  • Isotopes

    Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons.

  • Radioactive Isotopes

    Radioactive isotopes have unstable nuclei that decay spontaneously, releasing radiation used in medicine and research.

  • Electron Shells and Valence Electrons

    Electrons occupy shells around the nucleus; the outermost shell is the valence shell containing valence electrons involved in chemical bonding.

  • Inert Elements

    Inert atoms have complete outer electron shells and do not interact with other atoms.

  • Ionic Bond

    Ionic bonds form when one atom transfers electrons to another, creating oppositely charged ions that attract each other.

  • Covalent Bond

    Covalent bonds involve sharing of electrons between atoms to complete their valence shells.

  • Nonpolar vs Polar Covalent Bonds

    Nonpolar covalent bonds share electrons equally; polar covalent bonds share electrons unequally, creating partial charges.

  • Hydrogen Bond

    Hydrogen bonds are weak attractions between polar molecules involving hydrogen and electronegative atoms like oxygen or nitrogen.

  • Chemical Reaction

    A chemical reaction breaks existing bonds and forms new ones; reactants are starting materials, products are the results.

  • Cohesion and Adhesion of Water

    Cohesion is water molecules sticking together via hydrogen bonds; adhesion is water sticking to other substances.

  • Water's Role in Temperature Moderation

    Water absorbs and releases heat slowly due to hydrogen bonds, helping moderate temperature in organisms and environments.

  • Evaporative Cooling

    Evaporative cooling occurs when the highest energy molecules evaporate, lowering the temperature of the remaining liquid.

  • Density of Ice vs Liquid Water

    Ice is less dense than liquid water because hydrogen bonds form a stable 3D crystal structure that spaces molecules apart.

  • Water as a Solvent

    Water is a universal solvent that dissolves ionic and polar compounds, forming aqueous solutions essential for life.

  • pH Scale and Acids/Bases

    The pH scale measures acidity from 0 to 14; acids donate H+ ions, bases reduce H+ concentration.